The discovery of a complete 1.8 million-years-old skull has rewritten the story of how modern man evolved from our early ancestors in Africa, according to Swiss scientists.

A skull found in Georgia from an ancient human ancestor, known as Skull 5, implies that all Homo species were once one.

Research suggests that the earliest members of the Homo genus, including Homo habilis, Homo rudolfensis and Homo erectus belonged to the same species and simply looked different to each other, shaking up the classification system for early human ancestors.

The 1.8 million-year-old skull: The discovery of Skull 5 (pictured) has rewritten the story of how modern man evolved from our early ancestors in Africa, according to Swiss scientists. The skull, which was found in Georgia, implies that all Homo species were once one

The skull that was unearthed in Dmanisi, Georgia and was unlike other Homo fossils and combines a small braincase with a long face and large teeth. Pictured is a skull discovered in 2005 that is 1.5m years old

Unique: The skull were discovered alongside the remains of four other early human ancestors and a number of animal fossils

THE STORY OF SKULL 5

The skull was found in Dmanisi, Georgia and is from an ancient human ancestor

It combines a small braincase with a long face and large teeth, unlike other Homo fossils

Skull 5 was discovered alongside the remains of four other early human ancestors and some stone tools

All the items were found in the same location and date from the same time period

The skull suggests that the earliest members of the Homo genus, including Homo habilis, Homo rudolfensis and Homo erectus belonged to the same species and simply looked different to each other

Scientists said the skull belonged to a single Homo species that was able to cope with a variety of ecosystems after emerging from Africa some two million years ago

It is popularly thought that different characteristics among the Homo fossils showed they were distinct, different species but this research casts this theory into doubt.

Scientists from the Anthropological Institute and Museum in Zurichsay Skull 5 indicates that rather than several ecologically specialised Homo species, a single Homo species that was able to cope with a variety of ecosystems, emerged from Africa some two million years ago.

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They studied the skull that was unearthed in Dmanisi, Georgia and found that unlike other Homo fossils, Skull 5 combines a small braincase with a long face and large teeth.

It was discovered alongside the remains of four other early human ancestors, a variety of animal fossils and some stone tools, all of which are associated with the same location and time period which makes the find truly unique.

The site, which has only been partially excavated, is providing scientists with the first opportunity to compare and contrast the physical traits of multiple human ancestors that apparently coexisted at the same time in the same geological space.

The braincase of Skull 5 is only about 33.3 cubic inches (546 cubic centimeters), and suggests early humans had smaller brains despite modern human-like limb proportions and body size

The Dmanisi excavation site, situated below a medieval Georgian village, where the skull was found. It has only been partially excavated so far but has given scientists the first chance to compare how different human ancestors lived together

The differences between these Dmanisi fossils are no more pronounced than those between five modern humans or five chimpanzees, the scientists claimed.

The discovery suggests that early, diverse Homo fossils with their origins in Africa, actually represent variation among members of a single, evolving lineage - most appropriately Homo erectus.

Christoph Zollikofer from the Swiss museum said: 'Had the braincase and the face of Skull 5 been found as separate fossils at different sites in Africa, they might have been attributed to different species.

'That's because Skull 5 unites some key features, like the tiny braincase and large face, which had not been observed together in an early Homo fossil until now.'

David Lordkipanidze of the Georgian Academy of Sciences holds a 1.75-million-year-old skull, excavated in Dmanisi in 2001. The bones of an early human with a small head suggest larger brains associated with modern humans did not necessarily evolve before our ancestors began migrating

Given their diverse physical traits, the fossils associated with Skull 5 at Dmanisi can be compared to various Homo fossils, including those found in Africa, dating back to about 2.4 million years ago, as well as others unearthed in Asia and Europe, which are dated between 1.8 and 1.2 million years ago.

He added: 'The Dmanisi finds look quite different from one another, so it's tempting to publish them as different species.

'Yet we know that these individuals came from the same location and the same geological time, so they could, in principle, represent a single population of a single species.'

The hominid fossils from Dmanisi represent ancient human ancestors from the early Pleistocene epoch, soon after early Homo diverged from Australopithecus and dispersed from Africa, according to the study, published in the journal Science.

The jaw associated with Skull 5 was found five years before the cranium was discovered but when the two pieces were put together, they formed the most complete large skull ever found at the Dmanisi site.

For this reason, the researchers suggest that the individual to whom Skull 5 belonged was male.

The braincase of Skull 5 is only about 33.3 cubic inches or 546 cubic centimetres, however, which suggests that this early Homo had a small brain despite his modern human-like limb proportions and body size.

Professor Zollikofer added said: 'Thanks to the relatively large Dmanisi sample, we see a lot of variation.

'But the amount of variation does not exceed that found in modern populations of our own species, nor in chimps and bonobos,' he added.

'Furthermore, since we see a similar pattern and range of variation in the African fossil record...it is sensible to assume that there was a single Homo species at that time in Africa.

'And since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species.'

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